We propose to study development using the bacterium Myxococcus xanthus as a model system. Our specific objectives are: (a) To characterize myxobacterial hemagglutinin (MBHA), a development specific protein which peaks at the time of cellular aggregation. We plan to search for the MBHA receptor in the cell membrane and characterize it. (b) To isolate MBHA and protein S defective mutants of M. xanthus by direct screening of hundreds of developmental mutants in our collection. Mutants which are obtained will be characterized using biochemical, physiological and genetic techniques. (c) To study transcriptional regulation of development. The RNA polymerase from vegetative and developmental extracts will be studied on several templates in order to study developmentally regulated transcription in vitro.